Millisecond Forums

Sending TTL Codes Using Dell Legacy Extender/Windows 7

https://forums.millisecond.com/Topic13098.aspx

By jkrompi77 - 4/23/2014

Hi


I am attempting to get two copies of Inquisit talking to one another using TTL. Each copy is running on a Window 7 64bit Dell laptop, and the two are connected via a 25 pin parallel cable through Dell's legacy extender (my understanding is that it's essentially a port replicator). Within each computer, I appear to be able to access the parallel port using a separate piece of software that allows me to manually set various pins high/low, and I can verify that this is working using Inquisit's "receive" function in the port monitor - in other words, if I manually set pin 9 to "high" I am able to receive the code "128" in the Data Register (again, all within the same computer). However, I am unable to successfully send a TTL signal from one computer to the other using Inquisit's port monitor. Sending a code from one computer appears to have no effect on the other. Can anyone point me in the right direction? Are these port replicators incompatible with Inquisit? Is there any other solution for modern systems?
By Dave - 4/23/2014

> I appear to be able to access the parallel port using a separate piece of software that allows me to manually set various pins
> high/low, and I can verify that this is working using Inquisit's "receive" function in the port monitor - in other words, if I manually
> setpin 9 to "high" I am able to receive the code "128" in the Data Register (again, all within the same computer).

How do you verify that you are indeed physically accessing the parallel port using said software? It might just be emulating a port signal completely in software. In any case, if this indeed works as you think, you should be able to set a given pin to high on machine A and receive that signal on machine B.

The fact that the port monitor (in your within-machine scenario) shows a successful signal reception suggests that things are working fine on Inquisit's end.

Have you checked your port settings (LPT#, base address, etc. in the device manager) and verified you've set everything up correctly? Have you made sure the cable used to connect the machines is wired correctly (you'll probably want to find a LapLink-style crossover cable)?

> Are these port replicators incompatible with Inquisit?

I don't know anything about those replicators. It all depends on whether those Dell boxes expose a "true" parallel port, not merely some internal USB-to-parallel interface that's only sufficient to drive a legacy printer. Presumably Dell provides relevant technical specs somewhere online.

> Is there any other solution for modern systems?

Yes. Add-on cards (PCI, PCIe) are available that provide true parallel interfaces.
By jkrompi77 - 4/23/2014

Thanks for the prompt reply. A couple of follow-up questions:

Would you be able to point me to a laptop-based PCI parallel port card that's been shown to work with Inquisit? If possible, would you be able to make a similar recommendation for a laplink cable?
By Dave - 4/23/2014

> Would you be able to point me to a laptop-based PCI parallel port card that's been shown to work with Inquisit?

Unfortunately no -- the hardware market changes to quickly to make a concrete recommendation (specific models appear and disappear in short order). However, virtually any PCMCIA or ExpressCard along the lines of http://www.amazon.com/StarTech-com-ExpressCard-Parallel-Adapter-EC1PECPS/dp/B001Q7X0W6 should do the trick (merely provided as an example; not a recommendation for the particular device, which I do not own).

> If possible, would you be able to make a similar recommendation for a laplink cable?

Any will do -- "LapLink" here merely signifies the way those cables are wired (cf. https://en.wikipedia.org/wiki/LapLink_cable), i.e., how the pins on machine A's parallel port map to the pins on machine B's parallel port. It's likely you already have such a cable around.

In any case, any further insights re. your existing port replicators -- i.e., are you able to send a signal from machine A (using the software you mentioned to set specific pins hi/lo) to machine B?